'72 K5 - Greg's @MightAsWellK5 Build

[Greg72]

It was close to done before the frame modification started. I didn't have the clearance to sneak it past the engine without putting a big notch in the oilpan..... even that might not have worked 100%.

I was trying to keep the PHB behind the axle so that there would be less going on in front of it (draglink & tierod) but it looks like all 3 are going to have to peacefully co-exist up there somehow.


Maybe I should have Charlie do an illustration of how it's all going to fit?



-G

 

[folkenheath]

Well it looks like you made a lot more progress after some backwards progress. The panhard in the front is a little more conventional, make sure it's not in the way of the draglink, which will depend on your knuckle.

Also, I hate to point this out, but does this mean your PS frame modifications were in vein?

One idea, it may be strong enough the way it is, you'll have to judge that, but you can make the motor mount lighter with thinner material if you extend the side plates up and over the top of the flat plate the puck bolts too to reinforce the flat part which is loaded in the wrong direction. At the same time you could possibly get rid of the aluminum puck and make the whole thing lower.

Overall I like your progress, I want to see this thing on 4 wheels! Even if your shocks are some tubing for mockup.

Keep it up!

 

[Greg72]

Thanks Heath!

Yeah, I'll screw around with that motor mount one more time later on. I'm just getting tired of making the same parts over and over, so I will wait until I know for SURE that it doesn't need to be modified/cut/bent/tweaked a 7th time, and then I'll commit to a more elegant final iteration. The aluminum spacer is actually a "failsafe" placeholder in case I want to go with a taller motor mount in the future. The hard rubber ones I've got are certainly going to be strong enough, but once the truck is running (~2018 timeframe ) if the engine is really shaking the truck badly, I want to have the option to go with a set of fluid-filled mounts. Those tend to be taller, so I want to reserve some extra space now.

The frame mods gave me the clearance for the pumpkin, so I'd have had to do that no matter what. It turned out so well that I could probably try for 6.5" of bump travel if I wanted to. It all depends on how much clearance around the oilpan I'm comfortable with....

The PHB mount can certainly get beefier. I figure it can certainly be triangulated over to the pumpkin area for starters, plus the lower coilover mount is going to be just 4" from where that upper kingpin pivot is showing in the photo (there is a small breather hole that is just about the perfect spot), so all of that structure can be tied-in to create a larger, monolithic bracket. I was thinking about some through-holes in the large plate areas with tubes welded from both sides to give it more torsional strength, so that it wasn't just a big "hollow box" shape.

The draglink/tierod is going to be a puzzler. I really don't understand what sort of lengths to use for the arms to strike that balance between leverage and steering accuracy (you had talked about this previously). I am thinking of a PS steering arm like the ORD one, where the outermost hole holds the draglink, and the inner hole holds the tierod. This would allow me to consolidate the two heims (or 2 TREs) and simplify the packaging, but I don't understand exactly how this is all going to play out with my desire for correct Ackerman steering, or the built-in steering stops on the knuckles (which I would like to keep). Ideally, I want to maximize the turning radius that I've got... so I want to make sure that my steering allows me to go all the way to the steering stops in both directions. I know that when fully against the steering stops the inside wheel will be at 40* steering angle and the outer wheel will be at 30* at that same time.

One step at a time, I suppose. If I can get the PHB to work properly without interferences and keep it as tight to the axle as possible, then whatever space is left will have to be made to work for the steering.

-G

 

[folkenheath]

Thanks Heath!

Yeah, I'll screw around with that motor mount one more time later on. I'm just getting tired of making the same parts over and over, so I will wait until I know for SURE that it doesn't need to be modified/cut/bent/tweaked a 7th time, and then I'll commit to a more elegant final iteration. The aluminum spacer is actually a "failsafe" placeholder in case I want to go with a taller motor mount in the future. The hard rubber ones I've got are certainly going to be strong enough, but once the truck is running (~2018 timeframe ) if the engine is really shaking the truck badly, I want to have the option to go with a set of fluid-filled mounts. Those tend to be taller, so I want to reserve some extra space now.
-G

Fluid filled motor mounts, wow. I don't see why you would really need those, I think poly works pretty well for engine mounts. Sounds like potential complications where you don't need them, especially under the header. Although I would like to see the reaction if you told someone your motor mounts were leaking. That sounds like one of those trick questions....

What is an actual potential issue with Greg's rig (choose one):

a. squeaky exhaust belt
b. low blinker fluid
c. leaking motor mount
d. vibrating prefabulated amulite lunar wane shaft
e. faulty flux capacitor

 

[Greg72]

Fluid filled motor mounts, wow. I don't see why you would really need those, I think poly works pretty well for engine mounts. Sounds like potential complications where you don't need them, especially under the header. Although I would like to see the reaction if you told someone your motor mounts were leaking. That sounds like one of those trick questions....

What is an actual potential issue with Greg's rig (choose one):

a. squeaky exhaust belt
b. low blinker fluid
c. leaking motor mount
d. vibrating prefabulated amulite lunar wane shaft
e. faulty flux capacitor

f. Loose nut behind the wheel <- Figure out a way to solve this, and the rest of the issues take care of themselves.

I'm going into the shop tonight to mess around with that PHB mount some more. Quick "back of the napkin" calcs show that it should end up with only about 5.5* of downward slope, which is pretty good I think.







-G

 

[dremu]

What is an actual potential issue with Greg's rig (choose one):

a. squeaky exhaust belt
b. low blinker fluid
c. leaking motor mount
d. vibrating prefabulated amulite lunar wane shaft
e. faulty flux capacitor

You forgot the Illudium Q-36 Explosive Space Modulator.

And at least Greg isn't thinking about active motor mounts. Yet

-- A

 

[76zimmer]

Greg the backwards twostep seems to be quite productive as I'm sure you know
Seems like you get nowhere At times but the end result proves a better product because of it
I also subscribe to the pictures on paper too, that has saved me a few un thought of delays and rework

 

[blazinzuk]

d. vibrating prefabulated amulite lunar wane shaft

I believe it will be this, the problem of course is you need the recondite contrivance chamber to fix this. Which won't be a problem I am sure

 

[blazinzuk]

Oh yah get that dang steering box on man. Makes me a little worried about your steering, but I as I am sure you, have already identified at least 3 places you can bend cut shape that bar for clearance, which will also cause you to bend shape cut other brackets but oh well

 

[Greg72]

Oh yah get that dang steering box on man. Makes me a little worried about your steering, but I as I am sure you, have already identified at least 3 places you can bend cut shape that bar for clearance, which will also cause you to bend shape cut other brackets but oh well

Just got that done.... But I was delirious and put the steering arm on the wrong way (forward of the sector shaft instead of behind it)

I'll post pics in the morning. It's late.

What's a good starting point for hole spacing on a mock up steering arm? 6"? 7"?".


-G

 

[blazinzuk]

What's a good starting point for hole spacing on a mock up steering arm? 6"? 7"?".


-G

Get it on there first. I would say start long and then bring it back down if you need too.

its one of those things that I doubt it going to be the exact right length once you are done but should be really close. Plus I have never worked on mog steering. Well I built a full hydro bracket but thats all I did. Guy who owned it had it all figured out I just did all the fab and welding. Plus that was on a u1300 axle not 406 like yours

So you put the pitman arm on facing towards the front of the truck right?

Thats why I said use a Scout box, pitman arm goes towards the front of the truck not the back

 

[Greg72]

OK, here's the new PHB setup shown at ride height ( Eric, I took your advice and made the panhard bar mount NICE AND BIG to start off with)!!:

The PHB ended up at 39.25". I already cycled it and there are no clearance issues at full bump. As I alluded to last time, there's probably enough room to try for 6.5" - 7" of bump travel instead of the 6" I've got currently... Brandon would be proud.

... And here's the Scout box on the framerail:

The problem is that in the position it's in now, the draglink is going to be REALLY far out in front, so my steering arms are going to be a mile long. My thought was to push the box forward, and move the pitman arm behind it.... If I did it that way, I could get it really close to the PHB heim and keep the draglink setup a lot closer to the front of the axle (and therefore keep the steering arms to a more reasonable length)

Here's an example of what I was thinking (stolen from fishinnutt's build thread)

I think it was either you or Heath that mentioned that there was a "correct" way to setup the pitman arm (either forward or behind sector shaft) and it affects the geometry as it sweeps left-to-right during steering. I was left with the impression that the "wrong" way would give me some wacky bumpsteer or ???


EDIT:

Quick Google search for D60 high-steer arms got me this image from the Artec site:

Looks like a good dimension for starters would be 8" for the draglink, and around 6" for the tierod ends (as measured from the kingpin centerline)



-G

 

[folkenheath]

I think it was either you or Heath that mentioned that there was a "correct" way to setup the pitman arm (either forward or behind sector shaft) and it affects the geometry as it sweeps left-to-right during steering. I was left with the impression that the "wrong" way would give me some wacky bumpsteer or ???


EDIT:

Quick Google search for D60 high-steer arms got me this image from the Artec site:




Looks like a good dimension for starters would be 8" for the draglink, and around 6" for the tierod ends (as measured from the kingpin centerline)



-G

Either way will work fine Greg, technically if it pivots in the same direction as the knuckle (with the pivot in the back) it would be more perfect, but as you can see this is extremely difficult to do and you may not be able to tell the difference. Mine pivots in the front just like the picture you borrowed, and it works very well. Also, I haven't seen this "fishnut" thread, may have to check it out. Mine looks like this...

As for the pitman arm length. If you want to turn 40 degrees you should keep the ratio of the pitman arm vs knuckle arm the same as most crossover setups to start with. I don't have mine right now or I would tel you what it is, but the crossover arm and pitman arm were both from ORD and my ratio is perfect, just enough to get full turning but not too much that its too quick or harder to turn.

Also, an 8" draglink would be pretty short! I am guessing you meant pitman arm.

 

[Greg72]

I'm checking out a Pirate4x4 thread now on pitman arm dimensions (various)....

Looks like the hole spacing is anything from around 5.5" to something over 7" depending on the make/model of arm.

The fishinnutt thread is in the 69-72 1st Gen Forum.... you should like it, he put radius arms on it!!!


-G

 

[folkenheath]

Yeah in your borrowed picture I saw a nice fabricated pitman arm, panhard mount with dimple dies, radius arms, and a big block cylinder head peaking through, and I thought, I need to check that out.

 

[Greg72]

Couple more photos and comments....

Here's a shot from the front of the truck at ride height (please pardon the jungle gym of other bracing that's holding the frame up). In this image, the frame side PHB is set at 31" off the ground (second hole from top in plate). This gives the PHB a downward angle of 8*

In this shot, I dropped the frameside PHB mount 2" (to 29") to provide more clearance for the steering box. Obviously, I can't install the box as high as it's shown here because the splines don't extend down below the frame. Ultimately I'll need to cut a "saddle" into the frame area where the box goes to drop the whole thing down a few inches (hence the reason I figured I'd need to lower that PHB mount)

If I decide to go with the "rear swing" setup, then I should be able to raise that PHB mount back up to 31" since there won't be any interferences to worry about in that area.


EDIT:

I just plugged in the numbers for this PHB setup (at the 31" frame side PHB height).

Roll Axis = -1.11* (understeer)
Roll Center Height = 28.11" (vs. CG Height of 34")

If I can raise both sides by 2" the numbers improve to:

Roll Axis = -2.53* (understeer)
Roll Center Height = 29.44" (vs. CG Height of 34")


I'd always read that it's desireable to keep the roll center height as close to the CG-Height as possible. With these type of numbers I'm within 5 - 6" (roughly) which seems pretty good?






-G

 

[folkenheath]

I would just make the roll center as high as you reasonably can, and not worry about it. Your Cg is just a guess anyway since your truck isn't even done yet, you could be off by several inches.

Also, with the draglink that far forward it's going to make your knuckle pivot longer, which makes your ratio wrong, which means you need a longer pitman arm.........you see where this is going? You either need to move the steering box back quite a bit, or move it forward and pivot the pitman arm back.

 

[blazinzuk]

I would run the higher numbers. One cause it does seen to help our trucks to have higher RCH than alot of other types of cars. But remember as soon as your suspension height changes or one side compresses a bit this number changes so as long as its not too high or too low its not that big a deal.

Besides none of us really know the COG of our trucks, its a guestimate at best.

If your off on that number by even a couple inches than your RCH could be way off.

The higher the bar the shorter the bracket, the shorter the bracket the less strain on the frame.

I would do this because of the less strain.

When I first suggested the scout box I knew it would make the pahnard bracket difficult because I thought you would mount the box about 6" behind where you have it now.

Kind of figured it would be right in the way of the bracket there so having it as close to the frame as possible makes it easier to brace the bracket up with shall we say odd gussets that go around a steering box and pitman arm

What is your RCH in the rear?

 

[blazinzuk]

Its pretty obvious to me you aren't going to mount that steering box in a "simple" location. Its gonna get in the way of everything.

I kind of figured this.

 

[Greg72]

What is your RCH in the rear?

Rear Roll CG is 26.5" (Based on the same assumptions about Vehicle CG as the front suspension)...

That puts my front roll center a couple inches higher than the rear. IIRC, that is supposed to be the more stable way to do it???